What are the merits of a compressed load? I am working up some loads for a couple of rifle calibers and noticed that many that I am contemplating are compressed. Admitly, the idea of a compressed load worries me. Also, it has always been my belief that you need a little "air space" in the case for the gases to expand into when detonated.

Thanks,

------------------
Joe Portale
Tucson, Arizona Territory

"Those who turn their swords into plow shears,
end up plowing the fields of those who didn't"
Thomas Jefferson

To us slow-time humans, a gunshot seems like an explosion, but it's not. It might seem nit-picky, but while there is an explosive burst of sound (muzzle-blast), smokeless gunpowder does not detonate. Primers detonate; smokeless powder burns very rapidly.

Maybe it's reasonable to think that detonation is micro-seconds; very-rapid burning is milli-seconds. Okay. And we know that some powders are definitely faster burning than others.

Generally, compressed loads are done with the very-slow burn-rate powders. A compressed load still has a good bit of air space between the granules, plus IMR powder granules are hollow tubes.

FWIW, years ago I was reloading for a .270, using 4831. I merely scooped powder into the case until it was full, scraped the case-mouth level, and seated the bullet. With the 130-grain bullets, it probably wasn't a max-pressure load.

Art, with your background I am surprised you didn't mention this...so I will. In a car engine, the fuel/air mixture burns slowly. Detonation is a very bad thing. It's extremely hard on the engine. It's like hitting the piston dynamically with a hammer instead of forcing it statically down with your hand. Same with a cartridge. The powder burns an dproduces gasses -- that's what causes pressure which causes the bullet to go. In detonation, it all happens to fast. There is too much pressure too soon. The bullet/rifle cannot react quick enough, so somethign has to give -- usually the rifle.

Frankly, light loads with a lot of space scare me more than compressed.

Uncompressed blackpowder burns at the same or differnt rate than when compressed? I think it is the same...but not sure.

I just loaded 80 rounds of 7x57 with IMR-4350. The load is near max and is compressed. Compressed loads with log type powders seem to not give any problems. Ball powders get a bit squirrely whem you compress them. I don't compress ball powers. I do the others. (IMr 4350, 4831, H-4831 etc.)
Paul B.

This email link is to reach site administrators for assistance, if you cannot access TFL via other means. If you are a TFL member and can access TFL, please do not use this link; instead, use the forums (like Questions, Suggestions, and Tech Support) or PM an appropriate mod or admin.

If you are experiencing difficulties posting in the Buy/Sell/Trade subforums of TFL, please read the "sticky" announcement threads at the top of the applicable subforum. If you still feel you are qualified to post in those subforums, please contact "Shane Tuttle" (the mod for that portion of TFL) via Private Message for assistance.

This email contact address is not an "Ask the Firearms Expert" service. Such emails will be ignored. If you have a firearm related question, please register and post it on the forums.